This invention relates to liquid fuel burning appliances, and, more particularly, to a liquid fuel lantern which is equipped with an electronic ignition system.
Liquid fuel lanterns for camping and outdoor use are well known and are described, for example, in U.S. Pat. No. Re. 29,457, which is owned by The Coleman Company, Inc. Liquid fuel which is used in such lanterns can be Coleman fuel, white gas, unleaded gasoline, etc.
In conventional liquid fueled lanterns such as the ones which Coleman has offered for many years, fuel is contained in a pressure vessel or fuel tank into which air is pumped under pressure. As described in U.S. Pat. No. Re. 29,457, the fuel tank is equipped with a dip tube which extends to nearly the bottom of the tank. The dip tube is closed at the bottom with the exception of a small diameter orifice through which fuel is allowed to enter. The dip tube has an internal conduit which is open at the bottom and which communicates with the upper part of the fuel tank above the maximum intended fuel level. The dip tube orifice can be partly blocked by insertion of a needle which is suitably connected to the fuel control system so as to cause it to partly block the orifice during the lighting cycle and to leave the orifice unblocked during the normal burn cycle. The upper end of the dip tube is connected through a valve system to a generator. The generator is a metal tube which passes into a venturi tube which is connected to one or more catalytic mantles. Fuel is discharged at high velocity from an orifice at the end of the generator into the venturi where air is aspirated and mixed and fed to the catalytic mantle as a combustible mixture for burning.
Before the lantern is lit, the generator is cool, and fuel which flows through the generator is not vaporized. The unvaporized fuel which is discharged through the generator orifice is not readily ignitable at the mantle. To overcome this problem, a dip tube needle can be used to partly block the fuel entry orifice. This creates a pressure imbalance within the dip tube which permits pressurized air to flow through the passageway inside of the dip tube from above the fuel. This pressurized air mixes with the liquid fuel and moves with it to be discharged from the generator orifice. The fuel/air mixture which is discharged from the generator orifice consists of a fuel-vapor-laden air and atomized droplets of fuel which can be ignited at the mantle by a lit match.
After the fuel/air mixture which flows into the mantle is ignited, the generator will eventually be heated sufficiently to vaporize the fuel which flows through the generator. The fuel control system can then be adjusted to move the needle in the fuel entry orifice of the dip tube so that only fuel flows through the dip tube to the generator.
U.S. Pat. Nos. 4,870,314, 4,691,16, and 3,843,311 describe propane or LP lanterns which are equipped with piezoelectric ignition devices. Rather than using a lighted match, the LP gas is ignited by a spark which is generated by the piezoelectric device.
Liquid fuel lanterns are more difficult to light than LP lanterns. LP gas is gaseous at atmospheric pressure and temperature and is easily ignited by a spark, even under cold conditions.
On the other hand, liquid fuel is a liquid at atmospheric pressure and temperature. It is therefore more difficult to provide automatic spark ignition of the fuel/air mixture of a liquid fuel appliance, especially under cold conditions. As the fuel/air mixture flows into the mantle, it mixes with more air which makes the fuel mixture leaner. The lean fuel mixture is more difficult to light with a sparking device, and the difficultly increases as the ambient temperature decreases.